Generally, a compressor is an apparatus for compressing fluid by converting mechanical energy into kinetic energy. This compressor may be largely categorized into a hermetic compressor and a semi-hermetic compressor. In the hermetic compressor, a driving motor and a compression unit for compressing fluid by being operated by the driving motor are installed at one hermetic container. On the other hand, in the semi-hermetic compressor, the driving motor and the compression unit are installed at different hermetic containers.
The compressor may be also categorized according to a compression mechanism to compress fluid. For instance, the compressor may be categorized into a rotary compressor, a reciprocating compressor, a scroll compressor, etc. according to a compression mechanism. The reciprocating compressor serves to compress a refrigerant under configurations that a crank shaft is coupled to a rotor of a driving motor, a connecting rod is coupled to the crank shaft, and a piston coupled to the connecting rod performs a linear reciprocation in a cylinder.
FIG. 1 is a sectional view showing an example of a reciprocating compressor.
As shown, the reciprocating compressor comprises a casing 1 having oil contained at a bottom thereof, a driving motor 10 installed in the casing 1, a supporting unit 20 for elastically supporting the driving motor 10, and a compression unit 30 disposed above the driving motor 10.
The compression unit 30 includes a frame 31 elastically supported by the supporting unit 20, a cylinder block 32 integrally provided at the frame 31, a crank shaft 33 penetratingly-inserted into the frame 31 and forcibly-inserted into a rotor 12 of the driving motor 10, a piston 34 inserted into the cylinder block 32, a connecting rod 35 for converting a rotary motion of the crank shaft 33 into a linear reciprocation by connecting a cam portion of the crank shaft 33 to the piston 34, a valve assembly 36 coupled to the cylinder block 32, a discharge muffler 37 coupled to the cylinder block 32 so as to encompass the valve assembly 36, and a suction muffler 38 installed at the valve assembly 36 so as to be connected to the valve assembly 36.
Unexplained reference numeral 11 denotes a stator, F denotes an oil hole, and an SP denotes a suction pipe.
The operation of the reciprocating compressor will be explained as follows.
Once the driving motor 10 is operated, a rotation force of the driving motor 10 is transmitted to the crank shaft 33 to rotate the crank shaft 33. Then, a rotation force of the crank shaft 33 is transmitted to the piston 34 via the cam portion and the connecting rod 35. As a result, the piston 34 performs a linear reciprocation at an inner space of the cylinder block 32. Here, the valve assembly 36 is together operated to suck gas to the inner space of the cylinder block 32 through the suction muffler 38. The sucked gas is compressed, and then is discharged to outside of the casing 10 through the discharge muffler 37.
The oil contained at the bottom surface of the casing 1 is sucked through the oil hole (F) formed in the crank shaft 33 by rotation of the crank shaft 33. Then, the oil is supplied to components where sliding occurs to perform a lubrication operation, and then remains at the bottom surface of the casing 1.
The compressor constitutes a part of a refrigerating cycle apparatus which generates cool air by using a phase change of a refrigerant, and the refrigerating cycle apparatus is installed at a refrigerator or an air conditioner, etc. The refrigerator or the air conditioner has a different driving state according to a load. More concretely, when a large load is applied to the refrigerator or the air conditioner, the compressor has a large gas compression capacity. On the other hand, when a small load is applied to the refrigerator or the air conditioner, the compressor has a small gas compression capacity. When the compressor has a large gas compression capacity, the driving motor 10 of the compressor is operated in a high speed driving mode to increase a gas compression capacity. On the other hand, when the compressor has a small gas compression capacity, the driving motor 10 of the compressor is operated in a low speed driving mode to decrease a gas compression capacity. If the driving motor 10 rotates in a low speed (less than 45 Hz) due to a small gas compression capacity, the amount of oil pumped up through the oil hole (F) of the crank shaft 33 is reduced by a rotation speed of the crank shaft 33. This may cause oil to be supplied to components where sliding occurs with an insufficient amount. As a result, the components where sliding occurs are abraded, and thus are not smoothly operated. This may increase a frictional loss to lower the efficiency and to shorten a lifespan. To prevent this, an oil supply amount in a low speed driving mode may be increased through a structural change of the crank shaft.